Use of lasers for medical purposes is well established. Lasers are used extensively for cosmetic purposes such as hair removal, vein treatment, skin rejuvenation, treatment of telangiectasia and treatment of port wine stain. Each of these treatments is preferably performed with a laser producing laser pulses at a wavelength chosen to be most effective for the particular treatment. For example, a Nd:YAG laser operating at 1064 nm may be used for hair removal and certain types of vein treatment. A Nd:YAG laser operating at 1320 nm may be used for skin rejuvenation and micro skin surgery. Treatment of port wine stains is usually performed using a dye laser operating at a wavelength of 577 nm. Lasers used for treatment of small surface veins do not work very well for treatment of larger deeper veins. As a consequence a medical facility offering a variety of laser-based cosmetic services in the past has been required to acquire and maintain several separate laser systems. This is expensive.
Some wavelengths are very preferentially absorbed in a particular type of tissue such as when the tissue contains a particular chromophore that has a peak or relatively high absorption at the particular wavelength. Use of a laser beam matched to a peak or relatively high absorption in tissue to treat the tissue is referred to as xe2x80x9cselective thermolysisxe2x80x9d. Some wavelengths are absorbed relatively uniformly in tissue and when these wavelengths are used to treat the tissue it is referred to as xe2x80x9cnon-selective thermolysisxe2x80x9d or xe2x80x9chomogeneous thermolysisxe2x80x9d.
What is needed is a single laser that can produce simultaneously laser light at a variety of wavelengths needed in medical facilities specializing is cosmetic care.
The present invention provides a laser system in which the gain medium is an excited YAP:Nd crystal. The system is configured so that the crystal produces a twin laser beam comprising wavelengths at both 1079 nm and 1341 nm with substantial intensities at each wavelength. Optical components are described which establish the desired ratio of the intensities of the light at each of the two wavelengths. These ratios, I1079 nm/I1340 nm, may vary from about 0.1 to 10. In a preferred embodiment of the invention a kit including a YAP:Nd crystal and a specially coated output coupler is provided for converting an existing Nd:YAG laser system to a twin light laser capable of producing the above described twin laser beam. The Nd:YAG laser system is unable to produce simultaneously 1064 nm and 1320 nm at substantial intensities of both wavelengths. In another embodiment a special combination output coupler is provided which contains at least three partially reflecting mirror elements, one coated to reflect a substantial fraction of light at 1079 nm and pass light at 1340 nm, another mirror coated to reflect a substantial fraction of light at 1340 nm and pass light at 1079 nm and a third mirror coated to reflect a substantial fraction of light at both wavelengths. In one embodiment the mirror elements are mounted on a rotating frame so that the desired mirror element can be in the beam path to define the resonant cavity. By switching between mirrors the laser operator is able to produce laser beams at 1079 nm, 1340 nm or to produce a beam at a both wavelengths. A preferred embodiment produces a pulsed laser beam capable of providing fluences on the skin surface in the range of about 10 J/cm2 to 200 J/cm2 during a treatment period of less than 4 seconds.
A preferred application of this laser system is aesthetic medicine in which the two wavelength beam illuminates the skin and heats the skin relatively uniformly to a depth of a few millimeters. The skin surface is cooled during the process to prevent or minimize surface tissue damage while tissue beneath the surface is altered due to thermal effects.
This application also discloses techniques for producing other wavelengths from the two wavelength light produced by the YAP:Nd crystal.